Liquid detergent compositions, particularly concentrated liquid detergent compositions for laundry use, must be formulated for shelf-stability during manufacturing, distribution and consumption by the ultimate consumer.
Liquid detergent compositions are formulated with surfactants and other detergent active materials and detergency builders (typically comprising dissolved electrolyte) and, optionally, solid particles, which are dispersed in a continuous aqueous phase. The surfactant used in the liquid detergent compositions may exist in the form of lamellar droplets contained in a lamellar dispersion having a desirable turbid appearance and a sufficiently low viscosity to flow when poured by a consumer. Appropriate lamellar dispersions are described in U.S. Pat. No. 5,147,576, Montague et al., issued Sep. 15, 1992, which is hereby incorporated by reference.
The addition of materials such as the traditional polyacrylates or acrylate/maleate copolymers as builders or co-builders has been observed to disturb the desirable rheology of the lamellar dispersion required in liquid detergent compositions. The incompatibility of traditional polyacrylates and acrylate/maleate copolymers in liquid detergent formulations has been a particular problem in concentrated liquid detergent formulations. "Concentrated liquid detergent" formulations contain a higher percent surfactant or detergent active material than traditional liquid detergent compositions, i.e., at least about 25% detergent active materials.
U.S. Patent No. 5,147,576, discloses a deflocculating polymer consisting of a hydrophilic backbone with hydrophobic side chains which deflocculating polymer permits the formulation of concentrated liquid detergent compositions in the form of stable lamellar dispersions in a continuous aqueous phase. The deflocculating polymer permits incorporation of greater amounts of electrolytes than would otherwise be compatible with a liquid detergent composition having shelf-stability and the relatively low viscosity required by consumers. The deflocculating polymer provides stability in these liquid detergent compositions, whereas polymers traditionally used as stabilizers for emulsions do not perform as required in liquid detergent compositions.
It has now be found that liquid detergent compositions may be provided in a stable form comprising a lamellar dispersion of the detergent active materials in a continuous aqueous phase by the addition of a polymer having a hydrophilic backbone and a hydrophobic terminal group. Such a polymer may be economically and readily polymerized from materials such as acrylic acid and dodecyl mercaptan (DDM). Thus, these polymers provide a simple route to achieving stable liquid detergent compositions, particularly concentrated compositions.
Canadian Patent Number 971,299, issued Jul. 15, 1975, to Lamberti, et al., discloses the use in powdered detergents of an acrylate polymer, having at least one end of the polymer chain terminated with a sulfur-containing group or an hydroxy-containing group, as an organic builder. This builder is taught to be useful in place of phosphates. Copolymeric forms of the sulfur- group-terminated polymer are disclosed to be undesirable.
Thus, the benefits in liquid detergents of the hydrophobically-terminated, hydrophilic polymer disclosed herein are quite unexpected. In particular, the capacity of the polymers of this invention to maintain low viscosity, liquid phase stability and lamellar dispersions of surfactant in a continuous aqueous phase of a liquid detergent composition, particularly a concentrated composition, is unexpected.